SINKING manhole covers outside the Avon factory near Semington caused rush-hour chaos on Monday morning.

Heavy lorries and tractors thundering past the factory have caused the manhole covers, installed by factory contractors, to sink for the sixth time in 18 months.

Traffic lights were put up on Saturday as highway officials at Wiltshire County Council allowed work to be carried out by Trowbridge-based engineers Mowlem over the weekend.

But the traffic lights were still there on Monday with motorists facing huge queues stretching back into Melksham town centre.

Despite being cleared by Monday afternoon, council officials have warned the roadworks could be back within months because of the heavy volume of traffic on the road.

Don Jest, county council street works manager, said the work was due to have been finished by Sunday evening.

He said: "The traffic lights should have been down but they were still there on Monday. We will be speaking to the contractors and finding out what went wrong."

Highways area technician Dominic Gorton said more traffic chaos could be on its way in the future.

He said: "The trouble is we have 40-tonne lorries using the roads and the manholes are right on the wheel line. We won't have this problem once the bypass is built. There was nothing we could do and we have to put it down to experience."

Wessex Water is due to take over responsibility for the manholes and sewerage system next year, but only when they have been fully repaired.

Contractor Mowlem has said it was always going to finish work on Monday.

Contracts manager Chris Cloke said: "We always intended to finish on Monday, the council should have known. I think there has been a misunderstanding.

"We think we have cured the problem as we have been re-bedding and replacing the manhole covers."